Data.Acid.Local

AcidState container using a transaction log on disk. The term 'Event' is loosely used for transactions with ACID guarantees. 'Method' is loosely used for state operations without ACID guarantees (see Data.Acid.Core).

Documentation

openLocalState

Arguments

:: (Typeable st, IsAcidic st)

=> st

Initial state value. This value is only used if no checkpoint is found.

-> IO (AcidState st)

Create an AcidState given an initial value.

This will create or resume a log found in the "state/[typeOf state]/" directory.

openLocalStateFrom

Arguments

:: IsAcidic st

=> FilePath

Location of the checkpoint and transaction files.

-> st

Initial state value. This value is only used if no checkpoint is found.

-> IO (AcidState st)

Create an AcidState given a log directory and an initial value.

This will create or resume a log found in directory. Running two AcidState's from the same directory is an error but will not result in dataloss.

prepareLocalState

Arguments

:: (Typeable st, IsAcidic st)

=> st

Initial state value. This value is only used if no checkpoint is found.

-> IO (IO (AcidState st))

Create an AcidState given an initial value.

This will create or resume a log found in the "state/[typeOf state]/" directory. The most recent checkpoint will be loaded immediately but the AcidState will not be opened until the returned function is executed.

prepareLocalStateFrom

Arguments

:: IsAcidic st

=> FilePath

Location of the checkpoint and transaction files.

-> st

Initial state value. This value is only used if no checkpoint is found.

-> IO (IO (AcidState st))

Create an AcidState given an initial value.

This will create or resume a log found in directory. The most recent checkpoint will be loaded immediately but the AcidState will not be opened until the returned function is executed.

createCheckpointAndClose :: (SafeCopy st, Typeable st) => AcidState st -> IO ()

Save a snapshot to disk and close the AcidState as a single atomic action. This is useful when you want to make sure that no events are saved to disk after a checkpoint.